1. Field of the Invention
The present invention relates to a flexible tube which is used in an insertion portion of an insertion device inserted into a tube or the like, and which includes a spiral tube, and also to an insertion device having the flexible tube.
2. Description of the Related Art
For example, Jpn. Pat. Appln. KOKAI Publication No. 08-313820 discloses a flexible tube for use in an endoscope serving as an insertion device. The flexible tube includes a double spiral tube, a reticular body covering the double spiral tube, and an envelope layer covering the reticular body. The double spiral tube includes an inner spiral tube located on the inner side, and an outer spiral tube located on the outer side.
Each of the inner spiral tube and the outer spiral tube is spirally wound at constant pitches. A winding direction of the inner spiral tube is opposite to that of the outer spiral tube. At least one of an end portion of the inner spiral tube and an end portion of the outer spiral tube is formed as a densely wound portion.
For example, Jpn. Pat. Appln. KOKAI Publication No. 11-262470 discloses an insertion portion for use in an endoscope serving as an insertion device. A flexible tube of the insertion portion includes a spiral tube, a reticular body covering the spiral tube, and an envelope covering the reticular body. A wire guide is inserted through the flexible tube. The wire guide guides an operation wire inserted therethrough. The wire guide is made of a coil pipe, and the coil pipe is formed by densely winding a stainless steel wire such that the resultant winding has a constant diameter.
The wire guide is inserted into a flexibility-suppressing coil pipe (hereinafter referred to simply as a pipe). The pipe extends from a proximal end of the flexible tube to an intermediate point of the flexible tube. The pipe is formed by winding, like a coil, a thin metal wire, e.g., a stainless steel wire, such that the resultant winding has a constant diameter. In a distal end portion of the pipe, the winding pitch gradually increases in the direction toward the distal end, and the winding of the distal end portion becomes looser in that direction. With this structure, the flexibility changes smoothly at the intermediate point of the flexible tube.
For example, Jpn. Pat. Appln. KOKAI Publication No. 08-327915 discloses a flexible tube for use in an endoscope serving as an insertion device. The flexible tube includes a double spiral tube, a reticular body covering the double spiral tube, and an envelope layer covering the reticular body. The double spiral tube includes an inner spiral tube located on the inner side, and an outer spiral tube located on the outer side.
Each of the inner spiral tube and the outer spiral tube is spirally wound at constant pitches. A winding direction of the inner spiral tube is opposite to that of the outer spiral tube. A plate member forming the outer spiral tube is comparatively wide at a proximal end side and is comparatively narrow at a distal end side. With this structure, the flexible tube has high flexibility in a distal end side and has high rigidity in a proximal end side.